Duncan, 39, remained one of the very best big men in the NBA last season, averaging 13.9 points, 9.1 rebounds and 2 blocks while earning All-Star, All-NBA Third Team and All-Defensive Second team honors. Although the 55-win Spurs were unsuccessful in defending their 2014 title, falling in the first round to the Clippers, Duncan enjoyed another strong postseason, averaging 17.9 points, 11.1 rebounds and 1.4 blocks. Despite being one of the NBA's oldest players, Duncan ranked fifth among power forwards in Player Efficiency Rating, second in Real Plus-Minus and third in Win Shares, and SI.com ranked him No. 7 overall on our "Top 25 Free Agents of 2015" list.

​To say that Duncan's deal represents a significant sacrifice would be putting it mildly. If Duncan, a lifelong member of the Spurs, had actually entered the open market this summer, a four-year max contract offer wouldn't necessarily been out of the question, even at his age. At worst, a contender would have been willing to give him Greg Monroe money: $49.4 million over three years.

Instead, Duncan re-signs at a gifted rate that's even more team-friendly than the 3-year, $30 million deal he inked in 2012. Spurs management put the extra salary cap space to good use, of course, poaching All-Star forward LaMarcus Aldridge from the Blazers on a four-year maximum deal. By facilitating that move, Duncan gets a Twin Tower partner for a run at the 2016 title and a potential successor whenever he decides to hang them up. His give-back also helped San Antonio re-sign Kawhi Leonard (to a max deal), helped set up Danny Green's return on a below-market contract, and helped convince David West to sign on for some veteran's minimum ring-chasing. Duncan's franchise-changing talent is now paired with a truly franchise-building contract.

The $5 million salary figure should inspire guffaws even under these unusual circumstances. This summer's best salary comparison points for Duncan's contract are Derrick Williams (Knicks, $10 million over two years), Jonas Jerebko (Celtics, $10 million over two years), C.J. Watson (Magic, $15 million over three years), Mike Dunleavy (Bulls, $14.4 million over three years) and Kyle Singler (Thunder, $25 million over five years). San Antonio got a first-ballot Hall of Famer with plenty of game left at a journeyman's price.

Only one question remains: Will this sweetheart deal, like the last one, add another Larry O'Brien trophy to the coffers?